Wind turbines are devices that convert mechanical energy to electrical energy. A typical wind turbine includes a nacelle mounted on a tower housing a drive train for transmitting the rotation of a wind rotor to an electric generator and other components such as a yaw drive which rotates the wind turbine nacelle, several controllers and a brake. The wind rotor comprises a rotor hub supporting a number of blades extending radially therefrom for capturing the kinetic energy of the wind and causing the driving train rotational motion. The rotor blades have an aerodynamic shape such that when a wind blows across the surface of the blade, a lift force is generated causing the rotation of a shaft which is connected—directly or through a gearing arrangement—to the electrical generator. The amount of energy produced by wind turbines is dependent on the rotor blade sweeping surface that receives the power from the wind and consequently increasing the length of the blades leads normally to an increase of the power output of the wind turbine.
A variety of drive train configurations without gearbox are known in the art.
In one of these configurations, the tower is located between the rotor hub and the generator. One example of these configurations is disclosed in WO 01/94779 A1 in which the connecting arrangement between the rotor hub and the generator is a two-part axle supported by two bearing units. Another example is described in WO 02/33254 A1 in which the connecting arrangement between the rotor hub and the generator is a main shaft supported by means of two bearings arranged on a base at the top of the tower.
In another of these configurations, the generator, having a large-diameter rotor and stator, is located between the rotor hub and the tower and the connecting arrangement between the rotor hub and the generator is a hollow shaft supported by bearings on a tube member (interior to the hollow shaft) attached to the supporting frame of the wind turbine. One example of these configurations is described in US 2004/0108733 A1 in which the hollow shaft is supported by means of a single bearing which also carries moments on the tube member. This configuration is intended to reduce the size and the weight of the elements of the wind turbine which are to be mounted at the top of the tower but has the drawback of a costly maintenance in particular when the dismounting of components is needed.
DE 102004030929 B3 discloses another configuration having the generator placed upwind to the rotor. It is suggested that this configuration involves several advantages with respect to the configurations with the generator placed between the rotor hub and the tower such as, particularly, allowing the exchange of the generator without dismounting the wind rotor, reducing loads and lightening risks on the generator and facilitating the access to the rotor hub for maintenance purposes. It is not known however any commercial implementation because this configuration involves several problems.
One of them is that the replacement of small generator components such as fans or seals may require that service personnel has to access to the generator inside from the front side of the generator and thus also move the spare parts along this path. This means that service personnel has to climb on the outside of the wind rotor and generator rotor, an action that implies a number of problems and risks. The biggest risk is that personnel can fall down from the wind turbine, which has fatal consequences. Additionally the transfer of spare parts along this route is difficult.
This invention is intended to solve this problem.